Uber, the San Francisco startup known for letting people order private drivers in sleek black cars using a smartphone app, is offering an ice cream-on-demand service — for one day only — in 35 cities around the world, including New York, Philadelphia, London, Singapore and Rome.

Friday’s stunt, an expansion of last year’s ice cream promotion, comes in the midst of a sticky heat wave in New York City and elsewhere. Last year, people in seven U.S. and Canadian cities could use the Uber app to summon an ice cream truck hired by Uber to their location, provided they purchased a minimum number of treats. But demand exceeded supply, and not everyone who wanted ice cream got it.

“In San Francisco last year, we had so much demand that in order for everyone to get ice cream, we would have had to have 1,000 trucks on the road,” said Uber CEO Travis Kalanick. “That’s a city with 1,500 cabs.”

On normal days, Uber lets people order a ride in a taxi, a regular car, a high-end sedan or an SUV using its smartphone app, after they register for the service with their credit card information. Rates depend on where you are. In San Francisco, for example, a ride from the San Francisco airport to the city ranges from $50 to $85.

Kalanick, who co-founded Uber in 2009, said that although there is no way to meet all the demand for ice cream, “there is going to be crisp communication” that it is very limited supply.

But for those who do get ice cream, he added, it’s “a magical experience” to be able to push a button and summon an ice cream truck — or in the case of Italian cities, a gelato truck.

People will have to order more than one cone to have a truck come to them. Depending on the city, six ice creams will cost $20 to $35. The trucks will be out from 11 a.m. to 5 p.m. local time. Three cities — Miami, Houston and Portland, Ore. — will have the ice cream service available even though local laws don’t allow car-hailing apps like Uber to operate, Kalanick said. Uber is currently available in 35 cities, up from about a dozen at this time last year.

This is the second one-day promotion from Uber this summer. On July 3, the company offered to shuttle people to the Hamptons, the swanky seaside towns on New York’s Long Island, in a chopper at a cost of $3,000 for five people.

After Friday, those craving ice cream will have to resort to more traditional means of acquiring their treats.

“We are not going to be an ice cream delivery company,” Kalanick said.